$ A = \left[\begin{array}{rrr}0 & 2 & 2 \\ 0 & 2 & 0 \\ 2 & 2 & 1\end{array}\right]$ What is $ A^{-1}$ ?
Solution: $ = \left[\begin{array}{rrr}-\frac{1}{4} & -\frac{1}{4} & \frac{1}{2} \\ 0 & \frac{1}{2} & 0 \\ \frac{1}{2} & -\frac{1}{2} & 0\end{array}\right]$